Making leather efficiently

Redwood Comment

Published: 18 January, 2017

Mike Redwood

Do you remember the days when we started looking at the leather making processes using little symbols that showed us when the leather was being transported, inspected, delayed (the most frequent aspect), stored or actually processed? In fact, Process Flow charts were first introduced back in the 1920s but, true to its style of late adoption, the leather industry only got really enthusiastic about them in the 1960s and 1970s.

The long time that packs of leather were held here and there was what stood out, and tanners were active calculating how long it took to process leather if these were eliminated. In the excitement, big liming drums and concrete mixers were introduced to speed up unhairing and liming. The outcomes were not good. The importance of time in making good leather by these traditional means was being overlooked. In many spots where leather was apparently "hanging around" real processing was actually going on as chemicals penetrated and fixed, or moisture passed through and levelled out.

It took quite a long time to realise that the real delays were not in these stages but in holding stocks to ensure that no machine operator would run out of the work needed to maximise piecework earnings. The second reason for "delay" was indecision about the grading of leathers. Quite often this was because senior management did not accept the customers' opinion so held on to stock in the belief it could be sold at a higher price later. In one company I worked for, some of the stocks I found had been kept unsold for thirty years in the forlorn hope of a future sale at what was deemed as a "proper" price.

Rushing the chemical process did not help much either as at that time we did not know enough about the physical or chemical changes going on. Slowly more of this knowledge has come to light over the decades and we can see outstanding tanneries with flow systems and batch systems depending on the types of leather and product mixes required. Piecework ended as tanners realised that quality - properly designed to meet customer requirements - was more important than production for production's sake.

As chemical development has been slowed by the obsession with replacing chromium (rather false thinking in my view) and a huge requirement to meet new regulations like REACH, we have seen more and more focus on the physical and mechanical aspects. So now we have much better mechanical handling, more interconnected machines and increasing amounts of automation likely soon to include an element of artificial intelligence, or robotics. Italian machinery makers, Erretre, whom I had the opportunity to visit late last year, are working to understand better the way moisture exists and moves within the leather structure and reflecting the new knowledge in their machinery development. Some of the outcomes look likely to have a big impact.